API RECOMMENDED PRACTICE 534 SECOND EDITION, FEBRUARY 2007 REAFFIRMED, OCTOBER 2013 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Heat Recovery Steam Generators `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Heat Recovery Steam Generators Downstream Segment API RECOMMENDED PRACTICE 534 SECOND EDITION, FEBRUARY 2007 REAFFIRMED, OCTOBER 2013 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale SPECIAL NOTES API publications necessarily address problems of a general nature With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights API publications may be used by anyone desiring to so Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict API publications are published to facilitate the broad availability of proven, sound engineering and operating practices These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard API does not represent, warrant, or guarantee that such products in fact conform to the applicable API standard `,,```,,,,````-`-`,,`,,`,`,,` - Users of this recommended practice should not rely exclusively on the information contained in this document Sound business, scientific, engineering, and safety judgment should be used in employing the information contained herein All rights reserved No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C 20005 Copyright © 2007 American Petroleum Institute Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale FOREWORD Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in order to conform to the specification This document was produced under API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C 20005 Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years A one-time extension of up to two years may be added to this review cycle Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000 A catalog of API publications and materials is published annually and updated quarterly by API, 1220 L Street, N.W., Washington, D.C 20005 Suggested revisions are invited and should be submitted to the Standards and Publications Department, API, 1220 L Street, NW, Washington, D.C 20005, standards@api.org `,,```,,,,````-`-`,,`,,`,`,,` - iii Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale CONTENTS Page GENERAL .1 1.1 Scope 1.2 Referenced Publications 1.3 Definition of Terms 1.4 Regulatory Requirements FIRETUBE HEAT RECOVERY STEAM GENERATORS 2.1 General 2.2 Application .4 2.3 System Consideration 2.4 Advantages of Firetube Over Watertube Hrsgs 2.5 Disadvantages of Firetube Relative to Watertube HRSGs 2.6 Mechanical Description 2.7 Operational Description .17 WATERTUBE HEAT RECOVERY STEAM GENERATORS .18 3.1 General 18 3.2 Application .18 3.3 Gas Turbine Exhaust HRSG 19 3.4 Fired Heater Convection Section HRSG .37 3.5 FCC Regenerator Flue Gas HRSG 38 APPENDIX A APPENDIX B APPENDIX C `,,```,,,,````-`-`,,`,,`,`,,` - Figures 10 11 12 13 14 15 16 17 18 A-1 B-1 B-2 B-3 STEAM DRUMS 43 HEAT FLUX AND CIRCULATION RATIO 51 SOOTBLOWERS .55 Horizontal Firetube with External Drum HRSG Vertical Firetube with External Drum HRSG .4 Firetube Kettle Type HRSG Insulated Metal Ferrule Insulated Ceramic Ferrule .9 Conventional Strength Weld 10 Full-depth Strength Weld 10 Back (Shell-side) Face Weld .11 Channel-tubesheet-shell Interconnection 12 Dual Compartment Firetube HRSG 13 Two Tube Pass Firetube HRSG 14 Internal Bypass System with Valve and Dampers 14 Partially Tubed Firetube HRSG 16 Basic Tubular Arrangement 19 Interlaced Tubular Arrangement 19 Natural Circulation HRSG 20 Typical Natural Circulation Gas Turbine Exhaust HRSG 20 Typical Fire Heater Convection Section HRSG 38 Typical Steam Drum 43 Typical Watertube HRSG 53 Typical Circulation Rate 53 Typical Forced Circulation System 54 v Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale Page C-1 C-2 C-3 C-4 C-5 C-6 Sootblower Cleaning Lanes Typical Fixed Position Rotary Mounting Arrangement Typical Steam Flow Rate for Fixed Rotary Soot Blowers Typical Air Flow Rate for Fixed Rotary Soot Blowers Typical Retractable Mounting Arrangement Typical Steam Flow Rate for Retractable Soot Blowers `,,```,,,,````-`-`,,`,,`,`,,` - Tables Typical Pinch and Approach Temperatures A-1 Watertube Boilers Recommended Boiler Water Limits and Associated Steam Purity at Steady State Full Load Operation A-2 Suggested Water Quality Limits B-1 HRSG Firetube and Watertube Local Heat Flux vi Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale 55 56 57 57 58 59 24 44 45 52 Heat Recovery Steam Generators General 1.1 SCOPE The HRSG systems discussed are those currently in industry use A general description of each HRSG system begins Sections and Selection of an HRSG system for description does not imply other systems are not available nor recommended Many individual features described in these guidelines will be applicable to any type of HRSG system Appendices A, B, and C refer to Sections through 1.2 REFERENCED PUBLICATIONS 1.2.1 The editions of the following standards, codes and specifications that are in effect at the time of publication of this publication shall, to the extent specified herein, form a part of this publication API/ISO1 Std 530/ISO 13704 RP 536 Std 560/ISO 13705 Std 660/ISO 16812 ABMA2 Boiler 402 ANSI3/ASME4 ANSI 14.3 PTC 4.4 Petroleum and natural gas industries—Calculation of heater-tube thickness in petroleum refineries Post Combustion NOx Control for Fired Equipment in General Refinery Services Petroleum and natural gas industries—Fired heaters for general refinery service Petroleum and natural gas industries—Shell-and-tube heat exchangers for general refinery service Boiler Water Quality Requirements and Associated Steam Quality for Industrial/Commercial and Institutional Boilers Fixed Ladders—Safety Requirements Gas Turbine Heat Recovery Steam Generators Performance Test Code ASME Boiler and Pressure Vessel Code, Section I: “Power Boilers” and Section VIII, Division 1, “Pressure Vessels.” Consensus Operating Practices for Control of Feedwater/Boiler Water Chemistry in Modern Industrial Boilers CRTD–Vol 34 SA-106 Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service SA-178/SA-178M Standard Specification for Electric-Resistance-Welded Carbon Steel and Carbon-Manganese Steel Boiler and Superheater Tubes SA-214/SA-214M Specification for Electric-Resistance-Welded Carbon Steel Heat-Exchanger and Condenser Tubes STS-1 Steel Stacks ASTM5 D 1066-97(2001) Standard Practice for Sampling Steam NFPA6 8502 Standard for the Prevention of Furnace Explosions/Implosions in Multiple Burner Boilers 1International Organization for Standards, 25 West 43rd Street, Floor, New York, New York, 10036, www.iso.org 2American Boiler Manufacturers Association, 8221 Old Courthouse Road, Suite 207, Vienna, Virginia 22182, www.abma.com 3American National Standards Institute, 25 West 43rd Street, 4th floor, New York, New York, 10036, www.ansi.org 4ASME International, Park Avenue, New York, New York, 10016, www.asme.org 5ASTM International, 100 Bar Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org 6National Fire Protection Association, Batterymarch Park, PO Box 9101, Quincy, Massachusetts 02269-9101, www.nfpa.org Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - This publication provides guidelines for the selection or evaluation of heat recovery steam generator (HRSG) systems Details of related equipment designs are considered only where they interact with the HRSG system design This publication does not provide rules for design, but indicates areas that need attention and offers information and description of HRSG types available to the designer or user to aid in the selection of the appropriate HRSG system API RECOMMENDED PRACTICE 534 OSHA7 Applicable standards of the Federal Register’s Rules and Regulations TEMA8 Standards of the Tubular Exchanger Manufacturers Association 1.2.2 In addition, this publication draws upon the work presented in the following publications: Steam/Its Generation and Use, The Babcock & Wilcox Company, New Orleans, Louisiana Combustion Engineering—A Reference Book on Fuel Burning and Steam Generation, Combustion Engineering Co., Inc., Stamford, Connecticut A Bar-Cohen, Z Ruder, and P Griffith, “Circumferential Wall Temperature Variations in Horizontal Boiler Tubes,” International Journal of Multiphase Flow, Vol 9, No 1, pp – 12, February 1983 B Y, Taitel and A E Dukler, “A Model for Predicting Flow Regime Transitions in Horizontal and Near Horizontal Gas— Liquid Flow,” AICHE Journal, Vol 22, No 1, pp 47 – 55, January 1976 Guidelines for the Operation and Maintenance of HRSGs, HRSG User’s Group, Tetra Engineering Group, Weatogue, Connecticut 1.3 DEFINITION OF TERMS 1.3.1 approach temperature: The difference between the saturation temperature of the steam and the temperature of the water leaving the economizer 1.3.2 attemporator: See desuperheater 1.3.3 desuperheater: A device located internal or external to the HRSG that controls the exit temperature of the steam from the superheater The device typically injects pure water into the steam Also called an attemporator 1.3.4 downcomer: A heated or unheated pipe carrying water from the steam drum to an evaporator/generator section of an HRSG 1.3.5 evaporator: The portion of the HRSG in which water is boiling to form steam Typically a mixture of water and steam exists at the exit of this portion Also referred to as a steam generator section 1.3.6 firetube HRSG: A shell-and-tube heat exchanger in which steam is generated on the shell side by heat transferred from hot fluid flowing through the tubes 1.3.7 generator: The entire water/steam heating system portion of the HRSG Sometimes used synonymously as the evaporator section 1.3.8 heat recovery steam generator (HRSG): A system in which steam is generated and may be superheated or water heated by the transfer of heat from gaseous products of combustion or other hot process fluids 1.3.9 pinch temperature: The difference between the heating medium temperature leaving the steam generator section and the steam’s saturation temperature 1.3.10 process fluid: The heating medium used to supply the heat for steam generation to the HRSG 1.3.11 refractory design temperature: The hot face temperature for which the thickness of the lining shall be based upon It will normally include the user defined margin above the continuous operating temperature of the process 1.3.12 refractory rating temperature: The temperature at which the refractory material is acceptable for continuous use 1.3.13 refractory service temperature: The temperature established by the refractory manufacturer as the highest temperature for which the material is suitable This is normally the temperature at which the shrinkage of the material reaches its upper limit of about 1.5% 1.3.14 riser: A heated or unheated pipe carrying water and steam from an evaporator/generator section of an HRSG to the steam drum 7Occupational Safety & Health Administration, 200 Constitution Avenue, NW, Washington, D.C 20210, www.osha.gov 8Tubular Exchanger Manufacturers Association, 25 North Broadway, Tarrytown, New York 10591, www.tema.org `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale APPENDIX B—HEAT FLUX AND CIRCULATION RATIO B.1 General Circulation, heat flux and boiling flow regimes are fundamentals applicable to all HRSGs, regardless whether the system is forced or natural circulation, watertube or firetube design B.2 Heat Flux B.2.1 FILM BOILING Heat flux is the heat transfer rate per unit area of tube surface measured at the surface where boiling occurs If heat flux is excessive, steam is generated so rapidly that a steam film is formed at the tube wall This steam film displaces the water and keeps it from rewetting the tube This phenomenon is known as film boiling or departure from nucleate boiling and results in a sudden increase in the tube metal temperature This can cause tube failure resulting from high metal temperature The heat flux at which departure from nucleate boiling occurs depends on several variables including: a b c d Orientation and geometry of the surface Quantity of steam in the water Steam/water mixture velocity Pressure `,,```,,,,````-`-`,,`,,`,`,,` - The maximum heat flux allowed in HRSG design should be based on the most stringent combination of these variables B.2.2 NUCLEATE BOILING Since boiling heat transfer coefficients are much greater than that of the hot gas side, tube metal temperatures approach that of the saturated water This assumes nucleate boiling where steam bubbles generated at the tube wall are alternately displaced by water rewetting the tube Steam blanketing can also occur at low-heat fluxes with nucleate boiling if the forming steam bubbles are not continuously removed However, at heat fluxes above 1,262,000 W/m2 (400,000 Btu/h-ft2), nucleate boiling changes to film boiling At this point even the most vigorous circulation cannot prevent the formation of an insulating steam film on the heating surface For horizontal boilers, with tube bundles over 900 mm (36 in.) diameter, consideration should be given to providing vertical clear steam lanes within the bundle, together with large shell-to-bundle clearance to prevent steam blanketing B.2.3 LOCAL HEAT FLUX Table B-1 shows typical ranges of maximum allowable local heat fluxes The maximum heat flux should be calculated in the area of highest temperature difference based on fluid properties at that temperature and under clean conditions Both tubewall temperature and heat flux should be analyzed to determine the operating limits for HRSG Many industrial HRSG designs have much lower local heat fluxes than the maximum specified in Table B-1 This may be due to low-temperature difference or low overall heat transfer coefficients B.3 Circulation B.3.1 CIRCULATION RATIO Circulation ratio (CR) is the ratio of total steam and water flow in the circuit to the steam flow at the exit of the riser total riser steam and water mass flow rate CR = steam mass flow rate at riser outlet The designer sets the circulation ratio to maintain nucleate boiling for all operating conditions, that is, to avoid departure from nucleate boiling However, corrections for two-phase flow regime should be used in conjunction with circulation ratio rather than merely specifying minimum circulation ratio 51 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale 52 API RECOMMENDED PRACTICE 534 Table B-1—HRSG Firetube and Watertube Local Heat Flux HRSG Type Firetube Kettle Horizontal and Vertical Natural or Forced Circulation Thermosyphon Watertube Natural circulation Forced circulation Forced circulation Once-through [115 mm (4.5 in) max tube diameter] for enhanced oil recovery Heat pipe Natural circulation Maximum Allowable Local Heat Flux W/m2 (Btu/h-ft2) 78800 – 94600 (25000 – 30000) 220700 – 315500 (70000 – 100000) 315500 (100000) 126100 – 157600 (40000 – 5000) 126100 (40000) 157600 (50000) Comments • • • • • Pool boiling; circulation pattern is not well defined Tube spacing must be carefully considered for larger units Separate steam drum, well defined circulation pattern May not be applicable to transfer line exchangers in ethylene plants Higher fluxes possible in some proprietary designs • • • • • Vertical tubes prevent flow stratification Need to check circulation ratio at the exit of the hottest tube Design to avoid horizontal tubes stratification Need to control high-steam/water mixture velocity Need to control hardness of water used • Pool boiling • Circulation pattern is not well defined Bubble flow is the required two phase flow regime for HRSG tubes Bar-Cohen, Ruder, and Griffith found that undesired stratified or plug flow regimes are possible when circulation flow is either too low or heat fluxes too high Taitel and Dukler present a model predicting flow regimes as a function of tube diameter and orientation, fluid properties and steam/water mass velocity HRSG risers and downcomers form a flow circuit by connecting the steam drum at the top and a water drum or header at the bottom During operation, the steam/water mixture in the risers is less dense than the water in the downcomers Flow occurs within the circuit at a rate where the difference in static head between the risers and downcomers balance the resistance to flow A typical natural circulation circuit (typically, 15:1 to 20:1 circulation ratio) is shown in Figure B-1 The circulation ratio depends on the static head differences, resistance to flow in the circuit, system pressure, and quantity of steam generated The designer can increase circulation ratio by raising the height of the steam drum and/or by reducing flow resistance, for example, larger downcomers or increased flow area A typical performance curve for a particular system is shown in Figure B-2 This curve shows that an increase in the heat transfer and steam generation rate decreases the circulation ratio The circulation ratio should be calculated for the anticipated range of operation Low circulation ratio can result in departure from nucleate boiling and tube overheating Natural circulation HRSGs generally use vertical or inclined tubes to allow steam to rise freely B.3.3 FORCED CIRCULATION Forced circulation HRSGs use a pump to maintain circulation through the steam generating tubes of the evaporator, steam drum and headers A typical forced circulation circuit (minimum, typically, 10:1 circulation ratio) is shown in Figure B-3 Water is distributed to parallel tube circuits from an inlet header and the exiting steam/water mixture is collected in an outlet header The steam/water mixture is returned to the steam drum where the steam is separated and water is recirculated to the evaporator Steam generator tubes may have any orientation Fired heater applications are usually horizontal Tubes are connected in series in a serpentine arrangement to form each single tube pass With this arrangement water flows upward and improves flow stability between multipass parallel circuits The buoyancy of the two phase flow assists the forced circulation and minimizes the potential for steam pocketing Forced circulation HRSGs generally have larger tubes, longer tube circuits and higher flow resistance than natural circulation HRSGs Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - B.3.2 NATURAL CIRCULATION HEAT RECOVERY STEAM GENERATORS 53 Steam out Water in Steam generating tubes Downcomer Figure B-1—Typical Watertube HRSG `,,```,,,,````-`-`,,`,,`,`,,` - Circulation Ratio 20:1 15:1 10:1 0.6 0.7 0.8 0.9 1.0 1.1 Steam Rate Design Steam Rate Figure B-2—Typical Circulation Rate Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale 1.2 1.3 54 API RECOMMENDED PRACTICE 534 Steam out Water in Gas `,,```,,,,````-`-`,,`,,`,`,,` - Circulation pump Figure B-3—Typical Forced Circulation System B.3.4 ADVANTAGES/DISADVANTAGES B.3.4.1 Natural circulation advantages are: a No pumping systems are required b Less maintenance c More reliable B.3.4.2 Natural circulation disadvantages are: a Usually restricted to vertical or inclined tube applications b Usually installed at grade (more plot space required) c Steam drum location requires higher elevation B.3.4.3 Forced circulation advantages are: a Horizontal or vertical tube arrangements may be used b Forced circulation arrangements can be installed in vertical heater flue gas ducts c Smaller plot requirements The steam drum location is not restricted B.3.4.4 Forced circulation disadvantages are: a Pumping systems are required, including standby pump with automatic start b Higher maintenance due to pumps c Vertical tube arrangements require design expertise Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale APPENDIX C—SOOTBLOWERS C.1 General C.1.1 Flue gas side tube cleaning devices are primarily blowing media cleaners or sootblowers Sonic cleaning and shot cleaning are seldom used This appendix will address only sootblowers C.1.2 Sootblowers are either fixed position rotary or retractable type The retractable type may be either fully or partially retractable C.1.3 Fixed position rotary sootblowers have a multi-nozzle element permanently located within the flue gas stream The element is supported at both ends and within the flue gas stream by brackets usually attached to the tubes C.1.4 Retractable sootblowers have a lance that normally contains two nozzles, 180º opposed and located at its end The lance traverses across the tube bank while rotating The cleaning action is produced by directing the jets of blowing media in a helical path across the tube bank The lance is retracted outside of the HRSG when not in use Fully retractable type are not subject to the debilitating effects of temperature and foulants when not in service C.1.5 Sootblowers are placed in lanes between rows of tubes The sootblower lane is the free space between the nearest row of tubes upstream and downstream of the cleaning element See Figure C-1 Sootblowers Sootblower cleaning lanes Tubes Gas flow Figure C-1—Sootblower Cleaning Lanes C.2 Application C.2.1 Sootblowers are required when heavy oil is fired and extended surface tubes (studs or fins) are present Provisions for future cleaning are required when heavy oil is fired and only bare tubes are present Such provisions can include sootblower lanes or mechanical cleaning capability C.2.2 Sootblowers are required when catalyst bearing gases are present C.2.3 Provisions for future cleaning should be considered when light oil is the heaviest fuel fired C.2.4 Fuel gas fired units not normally require cleaning The fuel gas composition should be reviewed for fouling potential and future provision for sootblowers made when there is a remote possibility of fouling C.2.5 When ammonia and sulfur compounds are present, the potential for fouling and possible sootblower use should be considered 55 `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale 56 API RECOMMENDED PRACTICE 534 C.2.6 For temperatures over 540ºC (1000ºF), retractable blowers are desirable Rotary type is not desirable due to the potential oxidation and drooping of the rotary lance C.3 System Considerations C.3.1 HRSG DESIGN C.3.1.1 Internal refractories should be protected from damage by the blowing media Protection may include either metallic shrouds or dense castable lining for either cleaning lane and impingement area or the entire tube bank C.3.1.2 Inspection doors should be provided in the lanes to permit inspection of the tube surfaces C.3.1.3 Tube arrangement and extended surface choice and orientation should be compatible with the choice of sootblower C.3.1.4 The number of rows of sootblowers and the size of the sootblower lanes should accommodate the cleaning characteristics of the sootblower used C.3.1.5 The interference of tube supports, guides, baffles, etc must be considered when laying out cleaning devices C.3.1.6 The blowing media may be steam or air The manufacturer should be consulted as to the optimum pressure Operation at pressures lower than that recommended by the manufacturer decreases the cleaning ability of the sootblower Blowing pressure is typically 690 kPa(g) (100 psig) to 2,070 kPa(g) (300 psig) C.3.2 FIXED POSITION ROTARY SOOTBLOWERS C.3.2.1 Rotary sootblowers mounted on opposing sides of the tube bank are required if the tube bank exceeds 4.6 m (15 ft) C.3.2.2 Sootblower lanes should be a minimum of 90 mm (3.5 in.) clear between tube outside diameters for bare tube application, 250 mm (10 in.) between the tips of fins or studs when the sootblower element is parallel to the tubes, 450 mm (18 in.) when the element is perpendicular to the tubes C.3.2.3 Sootblower rotation is provided by a pneumatic or electric motor drive The element, combination gear drive, and cam actuated blowing media admission valve are shown in Figure C-2 C.3.2.4 Typical gas temperature limits for element materials are: `,,```,,,,````-`-`,,`,,`,`,,` - a Carbon Steel b Chrome plated or calorized steel c Stainless Steel (22% Cr minimum) 425ºC (800ºF) 540ºC (1000ºF) 815ºC (1500ºF) Typical housing with admission valve and gear drive Blowing medium outlet Casing Tubes Element Blowing medium inlet External mounting bracket Refractory lining Typical support brackets Figure C-2—Typical Fixed Position Rotary Mounting Arrangement Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale End support HEAT RECOVERY STEAM GENERATORS 57 C.3.2.5 Support brackets that are attached to tubes should be of the same material as the element In the event the bracket temperature exceed 1100ºF and the vanadium content of the fuel exceeds 50 ppm, 50 Cr-50 Ni (Cb) brackets should be used C.3.2.6 The support brackets should be independent of the element C.3.2.7 Support bracket spacing is a function of flue gas temperature Typical spacing limitations are as follows: a 1000 mm (40 in.) apart: b 750 mm (30 in.) apart: c 500 mm (20 in.) apart: 480ºC (900ºF) 815ºC (1500ºF) 980ºC (1800ºF) C.3.2.8 The number of nozzles for an element typically shown by Figure C-2 is based on providing one nozzle per space between tube rows After establishing the number of nozzles, the blowing media consumption per element may be estimated from Figures C-3 or C-4 Actual consumption rates are a function of sootblower construction details To provide adequate coverage for most industrial applications, multiple elements are normally installed Number of Nozzles (5/16” [8 mm] Venturi) 50 125 psig [862 kPa(g)] 40 100 psig [689 kPa(g)] 150 psig [1034 kPa(g)] 30 20 10 0 5000 (2268) 10000 (4536) 20000 (9072) 15000 (6804) 25000 (11340) Steam Consumption, lb/h (kg/h) Figure C-3—Typical Steam Flow Rate for Fixed Rotary Soot Blowers Number of Nozzles (5/16” [8 mm] Venturi) 50 125 psig [862 kPa(g)] 40 100 psig [689 kPa(g)] 150 psig [1034 kPa(g)] 30 20 10 0 1000 (28.3) 2000 (56.6) 3000 (85.0) 4000 (113.3) 5000 6000 (141.6) (169.9) 9000 10000 7000 8000 (198.2) (226.5) (254.9) (283.2) Air Consumption, SCFM (m³/min.) Figure C-4—Typical Air Flow Rate for Fixed Rotary Soot Blowers `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale 58 API RECOMMENDED PRACTICE 534 C.3.3 RETRACTABLE SOOTBLOWERS C.3.3.1 Cleaning lanes for bare tubes should be a minimum of 380 mm (15 in.) clear between tube outside diameters Cleaning lanes for extended surface tubes should be 460 mm (18 in.) between the tips of fins or studs when the sootblower element (lance) is parallel to the tubes and 610 mm (24 in.) when the element is perpendicular to the tubes C.3.3.2 The sootblower is supported at the casing wall by a sleeve yoke and from a platform or structure outside the casing near the outboard end Figure C-5 shows a typical support arrangement Sleeve yoke support Travel Support beam Lance Outboard support Feed tube Drive Head inlet end Nozzle head Figure C-5—Typical Retractable Mounting Arrangement C.3.3.3 Positive pressure wall sleeves with sealing air are required to prevent leakage of flue gases in positive pressure HRSGs C.3.4 SOOTBLOWER SPACING C.3.4.1 The spacing of sootblower elements should be based on the effective cleaning radius The effective cleaning radius is a function of the following: a b c d e f g h i Tube bank temperatures Blowing media Blowing media pressure Nozzle size and number Fuel characteristic (potential for soot formation) Tube arrangement (pitch) and size Extended surface type and orientation Orientation of sootblower element to tubes Type of HRSG C.3.4.2 Typical Sootblower spacing for staggered tube banks depends on whether the sootblower is a rotary or a retractable one For rotary sootblowers, the maximum horizontal or vertical coverage is 900 mm (3 ft) from the element or tube rows, whichever is less For retractable sootblowers, the maximum horizontal or vertical coverage is 1200 mm (4 ft) from the element or tube rows, whichever is less High fouling fuel will require more sootblowers The sootblower vendor should be consulted for his recommendations for the specific system and its effective cleaning radii Typical blowing steam consumption levels are given in Figure C-6 Air is rarely used in retractable sootblowers `,,```,,,,````-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale HEAT RECOVERY STEAM GENERATORS 35000 (15876) 300 psig [2068 kPa(g)] Steam Consumption, lb/h (kg/h) 30000 (13608) - in (25.4 mm) Nozzles 25000 (11340) 20000 (9072) 59 200 psig [1379 kPa(g)] - ¾ in (19 mm) Nozzles 15000 (6804) 100 psig [689 kPa(g)] 10000 (4536) 5000 (2268) 0 (0) 0.5 (3.23) (6.45) 1.5 (9.68) (12.90) 2.5 (16.13) (19.35) 3.5 (22.58) Figure C-6—Typical Steam Flow Rate for Retractable Soot Blowers C.3.5 EXTERNAL PIPING Sootblower external piping arrangements should include the following: a b c d Individual block valves to each blower Warm up piping Steam bleeds Steam traps C.3.6 CONTROLS Local start/stop push button stations, main steam control valve, and sequential control panel are normally provided by the sootblower manufacturer C.4 Advantages C.4.1 FIXED POSITION ROTARY SOOTBLOWERS The advantages of fixed-position rotary sootblowers include: a Construction is less complex b External platforms and structure minimized C.4.2 RETRACTABLE SOOTBLOWERS The advantages of retractable sootblowers include: a b c d The lance can be used at any flue gas temperature Internal supports are not required for the lance More effective cleaning is provided than with fixed position rotary sootblowers Fewer sootblowers are required than with fixed position rotary sootblowers Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,```,,,,````-`-`,,`,,`,`,,` - Effective Nozzle Area, in.² (cm²) 60 API RECOMMENDED PRACTICE 534 C.5 Disadvantages C.5.1 FIXED POSITION ROTARY SOOTBLOWERS The disadvantages of fixed-position rotary sootblowers include: a Elements are continually exposed to the flue gases b More frequent maintenance is required than with retractable sootblowers c Cleaning radius is short d Nozzles are subject to plugging e Rotary sootblowers are not recommended when the sootblower element sees temperatures in excess of 1100ºF or fuel oils containing large quantities of heavy metals (over 50 ppm vanadium) f Rotary sootblowers may not be suitable when certain high fouling fuels are employed C.5.2 RETRACTABLE SOOTBLOWERS The disadvantages of retractable sootblowers include: a b c d Significant platforms and structural supports are required More routine maintenance is required Flue gas seals are more susceptible to leakage More complex construction C.6 Operations Description Sootblowers operation frequency varies depending upon the equipment, the structure and orientation of the tube bank and the fouling tendency of the fuel Sequential operation of the sootblowers is required to prevent too great a load on utilities, and to prevent unstable operation of the HRSG due to excessive quantities of the blowing media being added to the flue gas `,,```,,,,``` Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale Effective January 1, 2007 API Members receive a 30% discount where applicable The member discount does not apply to purchases made for the purpose of resale or for incorporation into commercial products, training courses, workshops, or other commercial enterprises 2007 Publications Order Form Available through IHS: Date: ❏ API Member (Check if Yes) Invoice To (❏ Check here if same as “Ship To”) Ship To (UPS will not deliver to a P.O Box) Name: Name: Title: Title: Company: Company: Department: Department: Address: Address: Phone Orders: Fax Orders: Online Orders: 1-800-854-7179 (Toll-free in the U.S and Canada) 303-397-7956 (Local and International) 303-397-2740 global.ihs.com City: State/Province: City: State/Province: Zip/Postal Code: Country: Zip/Postal Code: Country: Telephone: Telephone: Fax: Fax: E-Mail: E-Mail: Quantity Title CX53005 Std 530/ISO 13704, Calculation of Heater Tube Thickness in Petroleum Refineries $176.00 C53502 Publ 535, Burners for Fired Heaters in General Refinery Services $103.00 C53602 RP 536, Post Combustion NOx Contol for Equipment in General Refinery Services $85.00 C53701 Std 537, Flare Details for General Refinery and Petrochemical Service $166.00 C56003 Std 560, Fired Heaters for General Refinery Services $189.00 CX66007 Std 660/ISO 16812, Shell-and-tube Heat Exchangers $116.00 CX66106 Std 661/ISO 13706-1, Air-Cooled Heat Exchangers for General Refinery Service $217.00 CX662101 Std 662, Part 1/ISO 15547-1, Plate Heat Exchangers for General Refinery Services $118.00 ❏ Payment Enclosed SO★ ❏ P.O No (Enclose Copy) ❏ MasterCard Total Subtotal Applicable Sales Tax (see below) ❏ Charge My IHS Account No ❏ VISA Unit Price Product Number ❏ American Express ❏ Diners Club ❏ Discover Rush Shipping Fee (see below) Shipping and Handling (see below) Credit Card No.: Total (in U.S Dollars) Print Name (As It Appears on Card): ★ Expiration Date: `,,```,,,,````-`-`,,`,,`,`,,` - 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